From 6fae3b477f80e422f62c75d8e6c39214c6c4915e Mon Sep 17 00:00:00 2001
From: Jan Supol <jan.supol@oracle.com>
Date: Fri, 25 Oct 2019 12:10:48 +0200
Subject: [PATCH 1/2] Performance improvement in
 Resource.Builder#mergeResources

Signed-off-by: Jan Supol <jan.supol@oracle.com>
---
 .../jersey/server/model/Resource.java         | 39 +++++++++++--------
 1 file changed, 22 insertions(+), 17 deletions(-)

diff --git a/core-server/src/main/java/org/glassfish/jersey/server/model/Resource.java b/core-server/src/main/java/org/glassfish/jersey/server/model/Resource.java
index c036413cc3..831e39cc1c 100644
--- a/core-server/src/main/java/org/glassfish/jersey/server/model/Resource.java
+++ b/core-server/src/main/java/org/glassfish/jersey/server/model/Resource.java
@@ -25,10 +25,13 @@
 import java.util.LinkedHashSet;
 import java.util.LinkedList;
 import java.util.List;
+import java.util.Map;
 import java.util.Set;
 import java.util.stream.Collectors;
 
 import javax.ws.rs.Path;
+import javax.ws.rs.core.MultivaluedHashMap;
+import javax.ws.rs.core.MultivaluedMap;
 
 import org.glassfish.jersey.Severity;
 import org.glassfish.jersey.internal.Errors;
@@ -543,27 +546,29 @@ private void onBuildChildResource(Builder childResourceBuilder, Resource.Data ch
         }
 
         private static List<Resource.Data> mergeResources(List<Resource.Data> resources) {
-            List<Resource.Data> mergedResources = new ArrayList<>();
-            for (int i = 0; i < resources.size(); i++) {
-                Resource.Data outer = resources.get(i);
-                Resource.Builder builder = null;
+            final MultivaluedMap<String, Data> resourceData = new MultivaluedHashMap<>();
+            final List<Resource.Data> mergedResources = new ArrayList<>();
 
-                for (int j = i + 1; j < resources.size(); j++) {
-                    Resource.Data inner = resources.get(j);
+            for (Iterator<Resource.Data> resourcesIterator = resources.iterator(); resourcesIterator.hasNext(); ) {
+                Resource.Data data = resourcesIterator.next();
+                if (resourceData.containsKey(data.path)) {
+                    resourcesIterator.remove();
+                }
+                resourceData.add(data.path, data);
+            }
 
-                    if (outer.path.equals(inner.path)) {
-                        if (builder == null) {
-                            builder = Resource.builder(outer);
+            for (Map.Entry<String, List<Resource.Data>> entry : resourceData.entrySet()) {
+                if (entry.getValue().size() == 1) {
+                    mergedResources.add(entry.getValue().get(0));
+                } else {
+                    Resource.Builder builder = null;
+                    for (Resource.Data data : entry.getValue()) {
+                        if (builder != null) {
+                            builder.mergeWith(data);
+                        } else {
+                            builder = Resource.builder(data);
                         }
-                        builder.mergeWith(inner);
-                        resources.remove(j);
-                        //noinspection AssignmentToForLoopParameter
-                        j--;
                     }
-                }
-                if (builder == null) {
-                    mergedResources.add(outer);
-                } else {
                     mergedResources.add(builder.buildResourceData());
                 }
             }

From 2deef247881d91e16a15c24168a7bf8ba8188f72 Mon Sep 17 00:00:00 2001
From: Jan Supol <jan.supol@oracle.com>
Date: Wed, 30 Oct 2019 09:42:18 +0100
Subject: [PATCH 2/2] Revert LinkedList->ArrayList to keep fast Iterator.remove

Signed-off-by: Jan Supol <jan.supol@oracle.com>
---
 .../main/java/org/glassfish/jersey/server/model/Resource.java   | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/core-server/src/main/java/org/glassfish/jersey/server/model/Resource.java b/core-server/src/main/java/org/glassfish/jersey/server/model/Resource.java
index 831e39cc1c..bb7961feb1 100644
--- a/core-server/src/main/java/org/glassfish/jersey/server/model/Resource.java
+++ b/core-server/src/main/java/org/glassfish/jersey/server/model/Resource.java
@@ -203,7 +203,7 @@ public static final class Builder {
         private Builder(final Resource.Builder parentResource) {
             this.methodBuilders = new LinkedHashSet<>();
             this.childResourceBuilders = new LinkedHashSet<>();
-            this.childResources = new ArrayList<>();
+            this.childResources = new LinkedList<>();
             this.resourceMethods = new LinkedList<>();
             this.handlerClasses = Collections.newSetFromMap(new IdentityHashMap<>());
             this.handlerInstances = Collections.newSetFromMap(new IdentityHashMap<>());